Integrated chips are formed by complex fabrication methods during which a workpiece is subjected to a plurality of different processes. Typically, the processes may include photolithography, implantations, etches, depositions, etc. For example, in a typical photolithography process, a surface of a semiconductor wafer is covered with a light sensitive (e.g., UV sensitive) photoresist material that is exposed and subsequently developed to selectively mask certain areas of the wafer. Unmasked areas of the wafer may then be processed (e.g., unmasked areas of the wafer may be selectively etched to pattern a layer underlying the photoresist) in a processing chamber. Once processing is completed, the photoresist material may be removed by an ashing process that utilizes a mixture of reactive gases, such as atomic oxygen, to remove the photoresist from the surface of the wafer.
The ashing process results in an effluent byproduct, having photoresist material, which is then removed from the processing chamber. If the effluent material is volatile, it is typically exhausted through scrubbing machines. However, under some resist removal conditions (such as oxygen-free plasma ashing) the photoresist effluent remains solid, and is effectively sublimated off the wafer. In such a case the solids entrained in the chamber exhaust tend to condense on any cold surface, such as the processing chamber walls, exhaust pipes, downstream valves (isolation and/or throttle), or even the large vacuum pumps.
In order to eliminate effluent buildup in the processing chamber, the processing chamber walls are typically heated above a certain temperature. While this prevents condensation in the chamber, it simply moves the condensate downstream to coat other components, preventing proper operation of valves and pumps. In order to minimize effects of this solid effluent, abatement systems using radio-frequency (RF) powered inductively coupled plasma sources may be configured downstream of the chamber to generate an abatement plasma that ‘burns’ away the effluent. FIG. 1 illustrates a typical downstream plasma ignition system. As shown in FIG. 1, a typical plasma ignition system 100 comprises a plasma chamber 102 inductively coupled to a commercially available RF power supply 104. The RF power supply 104 is configured to generate an RF signal operating at a set frequency (e.g., 13.56 MHz). Energy is transmitted from the RF power supply 104, via an antenna 110, to a plasma chamber 102, resulting in the ignition of an abatement plasma 108 when sufficient power has been delivered to the plasma chamber 102. Because the RF power supply 104 operates at an output power having an output impedance (e.g., 50 ohms) that rarely matches the load of the abatement plasma, a matching network 106 is configured to match the output impedance of the RF power supply 104 to a complex impedance established by the antenna 110 and abatement plasma load (i.e., the impedance of the plasma 108), thereby efficiently coupling power from the RF signal, generated by the RF power supply 104, into the abatement plasma 108.